The statements in this section merely provide background information related to the present disclosure and do not constitute prior art.
H.264/AVC is the latest video encoding and decoding standard with a utmost compression ratio among the video codecs that have been standardized to date. H.264/AVC seeks to increase the compression efficiency by using intra prediction modes considering directionality, 4×4 integer transform, various block modes from 16×16 to 4×4, a deblocking filter, etc.
H.264/AVC uses a weighted prediction (WP) technology to maximize the coding efficiency for images with changing brightness. WP is the technology for applying a weighting factor and offset in units of slices. The method of its application is expressed by Equation 1.Pidxd=widxd×Ridxd+oidxd  Equation 1
In Equation 1, P is the resulting video from applying WP to reference image R. ‘w’ and ‘o’ represent the weighting factor and offset, respectively. Subscripts ‘d’ and ‘idx’ respectively denote the predicted direction and reference index. A new reference image P made in this way is used to predict the current image. In addition, ‘w’s and ‘o’s that were used for every reference image R are encoded onto a slice header and transmitted to a decoder which then uses reference image R to generate reference image P after applying WP.
The inventor(s) has noted that known WP technologies for application in units of slices are designed to work with fade-in or fadeout effect of images and they cannot take into account factors such as local luminance variations from an illumination and changes in luminance due to motions of an object. Further, the inventor(s) has experienced that the coding efficiency is deteriorated when applying WP to the majority of images without noticeable brightness changes.